Chromosomal translocations that affect the proto-oncogene Mixed Lineage Leukemia (MLL) occur in aggressive human acute leukemias, both in children and adults (Sorensen et al., J Clin Invest., 1994. 93(1): p. 429-37., Cox, et al., Am J Clin Pathol., 2004. 122(2): p. 298-306., herein incorporated by reference in their entireties). They are particularly common in infants with acute myeloblastic leukemia (AML) and acute lymphoblastic leukemia (ALL) and constitute up to 80% of all infant acute leukemia cases. Fusion of MLL with one of 60 partner genes forms a chimeric oncogene which upregulates HOX genes resulting in a blockage of blood cell differentiation that ultimately leads to acute leukemia (Eguchi et al. Int J. Hematol., 2003. 78(5): p. 390-401., herein incorporated by reference in its entirety). Patients with leukemias harboring MLL translocations have a very poor prognosis (35% five year survival) and it is clear that novel therapeutic strategies are urgently needed to treat these leukemias (Slany. Hematol Oncol., 2005. 23(1): p. 1-9., herein incorporated by reference in its entirety). Menin is a critical cofactor in MLL-associated leukemias. Menin is a tumor-suppressor protein encoded by the Multiple Endocrine Neoplasia (MEN) gene. Menin is a ubiquitously expressed nuclear protein that is engaged in interactions with a cohort of transcription factors, chromatin modifying proteins, and DNA processing and repair proteins (Agarwal et al. Horm Metab Res., 2005. 37(6): p. 369-74., herein incorporated by reference in its entirety). The biological function of menin remains unclear and is context dependent. It functions as a tumor suppressor in endocrine organs (Marx. Nat. Rev Cancer., 2005. 5(5): p. 367-75., herein incorporated by reference in its entirety) but has an oncogenic role in myeloid cells (Yokoyama et al., Cell., 2005. 123(2): p. 207-18., herein incorporated by reference in its entirety). Association of menin with oncogenic MLL fusion proteins constitutively up-regulates expression of HOX genes and impairs proliferation and differentiation of hematopoietic cells leading to leukemia development. Myeloid cells transformed with oncogenic MLL-AF9 fusion protein require menin for efficient proliferation (Chen et al., Proc Natl Acad Sci USA., 2006. 103(4): p. 1018-23., herein incorporated by reference in its entirety). Menin is also required to maintain oncogenic transformation induced by other MLL translocations, including MLL-ENL, MLL-GAS7 and MLL-AF6 (Yokoyama et al., Cell., 2005. 123(2): p. 207-18., herein incorporated by reference in its entirety), demonstrating that menin functions as a general oncogenic cofactor in MLL-related leukemias and implies the interaction of menin with MLL fusions is a valuable target for molecular therapy. The leukemogenic activity of MLL fusion oncoproteins is dependent on association with menin. Therefore, selective targeting of this interaction could provide an attractive therapeutic approach to develop novel drugs for the MLL-related leukemias.